Transport Coefficients of Oligo- and Poly(α-methylstyrene)s in Dilute Solution

Abstract

The intrinsic viscosity [η] was determined for 25 samples of atactic oligo- and poly(α-methylstyrene)s (a-PαMS), each with the fraction of racemic diads f r = 0.72, in the range of weight-average molecular weight M w from 2.94 × 102 (dimer) to 3.22 × 106 in cyclohexane at 30.5 °C (ϑ). The translational diffusion coefficient D was also determined from dynamic light-scattering measurements for 21 of them in the range of M w from 5.30 × 102 (tetramer) to 3.22 × 106 under the same solvent condition. It is found that the double-logarithmic plots of [η] and M w D against M w follow their respective asymptotic straight lines of slope 1/2 for M w ≳ 2 × 105, but deviate upward and downward, respectively, from them with decreasing M w for smaller M w. From an analysis of these transport coefficients on the basis of the helical wormlike (HW) chain model, it is shown that the above M w dependence of [η] and D may be well explained by the corresponding HW theories with the values of the model parameters consistent with those previously determined from the mean-square radius of gyration 〈S 2〉. A comparison is also made of the present results for [η] and D for a-PαMS with the previous ones for atactic polystyrene with f r = 0.59, atactic poly(methyl methacrylate) (a-PMMA) with f r = 0.79, and isotactic PMMA with f r ≃ 0.01. It confirms the previous conclusion derived from 〈S 2〉 concerning the chain stiffness and local chain conformations of the a-PαMS chain. That is, the a-PαMS chain tends to retain large and clearly distinguishable helical portions in dilute solution just as the a-PMMA chain, although the strength of helical nature is somewhat smaller for the former.

Statistical and hydrodynamic properties of topological polymers for various graphs showing enhanced short-range correlation

“…In experiments the data points of the hydrodynamic radius versus the number of segments for linear polymers in a θ solvent are fitted by a curve with exponent ν = 0.484. [31,52] We also observe in Fig. 5 that the hydrodynamic radius R H (F ) of an ideal double-ring polymer of N segments is close to but slightly larger than that of an ideal θ-shaped polymer of N segments.…”

Dynamic Depolarized Light Scattering by Oligo- and Poly(α-methylstyrene)s in Dilute Solution

“…The values of the weight-average molecular weight M w determined from 1 H and 13 C NMR spectra, by analytical GPC, or from (static) LS measurements (in cyclohexane at 30.5 C), x w estimated from M w , the ratio of M w to the number-average molecular weight M n determined by analytical GPC, 3,6 and f r determined from 1 H and 13 C NMR spectra 3,7 are given in Table I. Although f r of the samples OAMS4-OAMS10 could not be determined because of the complexity of their 1 H NMR spectra, they may be regarded as having almost the same value of f r (0:71 .…”

“…In a new framework of polymer solution science on the basis of the helical wormlike (HW) chain model, 1,2 we have recently made a series of experimental studies [3][4][5][6] of dilute solution behavior of atactic oligoand poly(-methylstyrene)s (a-PMS) in the unperturbed  state. Specifically, we have determined the mean-square radius of gyration hS 2 i, 3 mean-square optical anisotropy hÀ 2 i, 4 scattering function, 5 and steady-state transport coefficients 6 in cyclohexane at 30.5 C (Â), 3 using well-fractionated a-PMS samples with the fraction of racemic diads f r regulated to be 0:72 AE 0:01.…”

“…Specifically, we have determined the mean-square radius of gyration hS 2 i, 3 mean-square optical anisotropy hÀ 2 i, 4 scattering function, 5 and steady-state transport coefficients 6 in cyclohexane at 30.5 C (Â), 3 using well-fractionated a-PMS samples with the fraction of racemic diads f r regulated to be 0:72 AE 0:01. 7 The results obtained have been analyzed to show that the a-PMS chain has rather large chain stiffness and strong helical nature like the atactic poly(methyl methacrylate) (a-PMMA) chain with f r ¼ 0:79.…”

Fine characterization of oligomers and polymers in dilute solution

“…Fig. 7 shows double-logarithmic plots of ½Z (in dL/g) against weight-average molecular weight M w for a-PaMS [17] and a-PS [8,18,19] in their respective Y states. respective Y states, where Z 0 is the viscosity coefficient of the solvent, k B the Boltzmann constant, and T the absolute temperature.…”